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J Thorac Cardiovasc Surg 1998;116:1015-1021
© 1998 Mosby, Inc.
SURGERY FOR ADULT CARDIOVASCULAR DISEASE |
From the Departments of Cardiac Surgerya and Cardiology,b Catholic University, and the Department of Cardiology, Campus Biomedico University,c Rome.
Received for publication May 20, 1998. Revisions requested July 20, 1998.Revisions received Aug 17, 1998. Accepted for publication Sept 8, 1998. Address for reprints: Gianfederico Possati, MD, Divisione di Cardiochirurgia, Policlinico Universitario A. Gemelli, Largo A. Gemelli 8, 00168 Rome, Italy.
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Abstract |
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 Top Abstract IntroductionPatients and methodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionPatients and methodsResultsDiscussionReferences |
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1 use of the radial artery (RA) in coronary artery bypass grafting was again proposed by Acar and colleagues in 1992. 2 Since then many groups have reported encouraging short-term results with this alternative arterial conduit. 3-7 To date, however, no published studies have examined the midterm angiographic fate of RA grafts used for myocardial revascularization.
Our experience with the use of the RA started in January 1993, and the early clinical and angiographic data from the first 109 cases were published in 1996. 8 We report here the 5-year clinical and angiographic results of the first 68 consecutive surviving patients in whom the RA was used as a free graft proximally anastomosed to the aorta.
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Patients and methods |
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TopAbstractIntroductionPatients and methodsResultsDiscussionReferences |
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8 In this report we analyze the midterm (5-year) results of the clinical and serial angiographic studies performed on the first 68 consecutive surviving patients in whom the RA was used as a free graft proximally anastomosed to the aorta. The main preoperative characteristics and operative data of these 68 patients are summarized in Tables I through III. Most of the patients were men, were in their sixth decade, and had triple-vessel coronary artery disease. The mean ejection fraction was almost normal (0.67), and only 8 patients were operated on for unstable angina.
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Follow-up
This study protocol was approved by the ethics committee of the Catholic University. Informed consent was obtained from all participating patients.
Patients were regularly followed up at our institution. They were required to undergo stress myocardial thallium 201 scintigraphy 6 months and 1 year after the operation and then every year thereafter. After the first year study, patients without either scintigraphic evidence of ischemia in the RA territory or angiographic demonstration of occluded RA graft (n = 60) were randomly assigned to continue (29 patients) or suspend (31 cases) the therapy with calcium-channel blockers.
In addition, all patients were asked to undergo a continuous-wave Doppler evaluation of the forearms and an angiographic study at 5 years' follow-up. Because of the observation reported by Acar and colleagues 2 that RA grafts judged to be occluded at early angiography were found to be patent at a successive examination, we decided that even patients with early angiographic evidence of occluded RA grafts should undergo angiography again at midterm.
Continuous-wave Doppler evaluation of the forearm. Continuous-wave Doppler evaluation of the forearm was performed according to a previously described method. 9 The peak systolic velocity (PSV), end-diastolic velocity, and resistance index of the brachial artery, ulnar artery, main artery of the thumb, and second and third common palmar digital arteries of each arm were calculated, as were those values for the RA of the side not operated on.
Angiographic study. Angiography was usually performed with 5F catheters inserted through the femoral artery. A complete study of the coronary arteries and of all the implanted grafts and a left ventriculography were performed in all patients. Attention was paid to the exact correspondence of the different projections between the preoperative evaluation and all the subsequent angiographic evaluations. RA graft status at both studies was classified into 4 subgroups: (1) perfect patency, (2) patency with irregularities, (3) string sign (defined as severe and extensive narrowing of the whole body of the graft), and (4) occlusion.
In a subgroup of 19 patients the in vivo responses of the RA and left ITA grafts to the endovascular infusion of serotonin were evaluated in both early and midterm angiographic studies. For this purpose serotonin hydrochloride was selectively injected into the 2 grafts at increasing concentrations (10–6 and 10–5 mol/L) at a rate of 3 mL/min for 3 minutes. At the end of the procedure, 2 mg isosorbide dinitrate was injected into the conduits.All measurements on angiographic images were performed with quantitative computerized angiography (Medis; Amsterdam, The Netherlands). Because this system has a lower detection limit of 0.6 mm, structures with smaller value were considered to be 0.6 mm in diameter. Measurements of graft diameter were always carried out about 10 mm above the distal anastomosis and were carried out separately by 2 different observers blinded to treatment.
Statistical analysis
Data are expressed as mean ± 1 standard deviation. Categoric variables were compared by the Fisher exact test, whereas the Student t test was used for quantitative data. RA diameter changes in response to the serotonin challenge were expressed as the percentage differences from the baseline values. RA diameters at baseline and in response to 10–5 mol/L and 10–6 mol/L serotonin were compared with 2-way analysis of variance for repeated measures. For F values with P < .05, pairwise comparisons were then performed with the Newman-Keuls t test for paired data. Only RA responses to the highest (vasoconstrictive) dose of serotonin were considered in this report.
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Results |
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TopAbstractIntroductionPatients and methodsResultsDiscussionReferences |
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Two patients died of noncardiac causes (liver and colon cancer 20 and 38 months after the operation, respectively) whereas no cardiac-related deaths were reported. Among the 66 surviving patients, 60 (90.9%) were free of angina. Five of the 6 patients in whom angina recurred underwent repeated angiography; 1 patient refused any invasive procedures. In the 5 patients who underwent further study, the causes of angina were as follows: progression of the atherosclerotic disease in ungrafted coronary vessels (2 cases, 23 and 31 months after the operation), stenosis of RA graft (1 case, 54 months after the operation), occlusion of ITA graft in the presence of patent RA graft (2 cases, 16 and 22 months after the operation).
Patients with RA stenosis and progression of the native coronary arteries successfully underwent percutaneous stent angioplasty (Fig. 1), whereas the 2 patients with ITA occlusion required reoperation. All 5 patients then underwent further studies after the surgical or percutaneous procedure for the midterm follow-up.
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Stress myocardial scintigraphy was performed in 61 cases; 5 patients without symptoms refused to undergo this investigation. Scintigraphic evidence of myocardial ischemia was detected in 16 of these 61 cases; 6 of these patients had clinical angina recurrence (as described previously), whereas 10 had asymptomatic ischemia. Silent ischemia was due to occlusion of a non-RA graft in 7 cases (5 saphenous veins, 1 right ITA, and 1 gastroepiploic artery) and to failure of RA conduit in 3 cases. In the absence of clinical ischemia, all these cases were treated medically.
With respect to the forearm status, no cases of ischemic hand complications were reported. However, 18 patients reported slight paresthesias (presumably from surgical damage to minor branches of the radial nerve) and 1 patient had tension at the elbow bend during forearm overextension (probably related to an excessive length of the skin incision). The remaining 47 patients (71.2%) were totally free of symptoms.
Doppler results
Doppler evaluation of the forearm was performed in 35 patients at a mean interval of 57 ± 8.4 months after the operation. The main Doppler results are summarized in Table IV. No important differences were reported with respect to mean PSV, end-diastolic velocity, and resistance index of the brachial artery and the second common palmar digital artery between the arm that was operated on and the contralateral arm.
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A flow gradient between the arteries of the hand of the arm that was operated on (flow higher in the medial and lower in the lateral arteries) had been seen 1 year after the operation, as has been described elsewhere. 9 This gradient had disappeared at 5 years' follow-up. At that time the PSVs in the main artery of the thumb and the second and third common palmar digital arteries were almost equivalent between the 2 arms.
Angiographic results
Midterm angiographic studies were performed in 61 of the 66 cases. Four patients refused any invasive procedure (3 of these had no symptoms and the fourth had Canadian Cardiovascular Society class III effort angina and scintigraphic evidence of ischemia in the distribution of a saphenous vein graft). One patient was excluded because of rapidly deteriorating renal function. As in 1 patient the RA was divided in 2 separate conduits, a total of 62 RA grafts were investigated. The mean interval between operation and angiography was 59 ± 6.5 months.
The main angiographic results are reported in Table V. The perfect patency rate of the RA was 87.0% (54/62), compared with 68.9% for the saphenous vein and 98.2% for the left ITA (P = .4 and P = .7, respectively). A string sign of RA grafts was reported in 2 cases.
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8 The comparison between the 2 angiographic studies performed in these 48 patients 1 and 5 years after the operation demonstrated that all RA grafts that were patent early after the operation remained patent at midterm follow-up (Table VI). Parietal irregularities of the proximal part of the RA graft (in close proximity to the aortic anastomosis) revealed in 7 cases by early angiography had disappeared after 5 years, and in 1 case the RA was judged to be occluded after 1 year but was found to be widely patent at midterm study (Fig. 2 and 3). For these reasons the perfect patency rate of RA grafts increased from 67.3% to 83.6% between the first angiographic study and the second (Table VI
). Moreover, the mean caliber of the RA grafts increased markedly between the 2 angiographic studies, from 2.09 ± 0.51 mm at 1 year after the operation to 2.58 ± 0.63 mm at 5 years' follow up (P < .001).
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70%) had string sign (1 case) or occlusion (4 cases) at midterm follow-up (Fig. 4). These 5 failures accounted for most of the overall cases of RA malfunction. The only case of occlusion among the patients in whom the RA was anastomosed to a vessel with stenosis greater than 70% was reported for a patient who had a severe mediastinitis early after the operation and underwent complete sternectomy and chest closure with a pectoralis major muscle flap.
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8 In 15 of these 19 cases, the same study was repeated at 5 years' follow-up. Comparison of results between the early and midterm studies showed that the vasoreactivity of RA grafts varied markedly between the first and the second angiographic investigations. In fact, early after the operation serotonin infusion led to a marked vasoconstriction of RA grafts (greater than that reported in the left ITA in the same patient), whereas after 5 years serotonin at the same doses elicited only minor RA constriction (similar to that reported in the ITA graft in the same patient; Table VII).
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Discussion |
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TopAbstractIntroductionPatients and methodsResultsDiscussionReferences |
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2-7 little is known about the results of RA grafts at midterm follow-up. The effective role of this conduit in coronary surgery and its relative value with respect to other arterial grafts and to venous grafts have not yet received objective clarification. The excellent overall survival and cardiac death–free survival 5 years after the operation testify to the good cardiologic and systemic status and the relatively young age of this population consequent to our policy of using RA grafts in young patients in good condition, who provide the optimal clinical setting for the evaluation of a new arterial conduit and who are expected to receive the maximal benefit from arterial revascularization.
In our experience the overall and perfect patency rates of RA grafts at 5 years' follow-up (91.9% and 87.0%, respectively) were slightly inferior to those achieved with the left ITA (100% patency rate and 98.2% perfect patency rate). However, because the left ITA was always used to graft the left anterior descending coronary artery (Table III), whereas the RA was usually anastomosed to secondary target vessels, the comparison of the angiographic results of these 2 conduits is marred by an obvious selection bias. In contrast, the saphenous vein had a target-vessel pattern more similar to that of the RA (Table III), so the comparison of the angiographic patency rates of these 2 conduits is probably more meaningful. Five years after the operation, the patency and perfect patency rates of the saphenous vein grafts were 74.1% and 68.9%, respectively. These rates are consistent with those reported in most angiographic series 10-12 and inferior to those achieved with the RA.
The serial angiographic study performed in the 48 patients who underwent both early and midterm repeated angiographic evaluation demonstrated that most of the parietal irregularities observed in RA grafts 1 year after the operation had disappeared at 5 years' follow-up, leading to an evident increase of the midterm perfect patency rate (Table VI). This observation led us to hypothesize that the abnormalities seen at early angiography were due to focal conduit spasm (rather than organic lesions), which resolved at midterm follow-up as a result of progressive loss of the RA hyperreactivity. In fact, although a high propensity toward spasm of RA grafts in the early postoperative period was demonstrated by our group in vivo 13 and episodes of spasm are reported in almost all the short-term angiographic series, until now no data on the modification with time of the RA vasoreactivity have been published.
In the subgroup of patients who underwent endovascular administration of serotonin at both the early and midterm angiographic studies, we observed a marked reduction in the contractile response of RA grafts. RA grafts had become almost insensitive to serotonin by 5 years' follow-up (Table VII). Concordantly, we observed that both the clinical results and the midterm angiographic statuses of the RA grafts were not influenced by the use of calcium-antagonists after the first postoperative year.
In recent years several experimental and angiographic observations have underscored the importance of the site of the proximal anastomosis of the free grafts. 4,14 It has been hypothesized that RA grafts proximally anastomosed to the ascending aorta are particularly vulnerable to the development of fibrous intimal hyperplasia because of the high wall stress to which they are exposed. 4 In fact, intimal hyperplasia was proposed as the main cause of the high rate of RA failure in the 1970s. 15
Our series shows that the angiographic results of RA grafts anastomosed to the aorta are excellent. Moreover, the evident increase with the time of RA graft diameter seems to deny the possibility of the development of a more than trivial degree of intimal hyperplasia. In addition our study testifies to the influence of the severity of target-vessel stenosis on the midterm patency of RA grafts. In fact, in our experience 4 of the 5 occlusions and 1 of the 2 string signs occurred during the first year in patients in whom the RA was used to revascularize a vessel with subcritical (<70%) stenosis, whereas the conduits anastomosed to severely stenotic arteries had clearly superior patency and perfect patency rates (Fig. 4).
It seems then likely that, in contrast to what has been reported for other conduits, 16 chronic native flow competition in the early postoperative period (when the RA is highly reactive, despite therapy with calcium-channel blockers) 13 can lead to RA graft malfunction and even failure (presumably from persistent graft spasm). In subsequent years the progressive loss of RA hyperreactivity can probably lead to spasm resolution and thus to disappearance of conduit irregularities and even reopening of previously closed grafts.
Finally, most patients are free of hand complications 5 years after the operation. Doppler studies of the forearm demonstrated that the removal of the RA was compensated for by an anastomotic network from the ulnar artery.
Our data show that the midterm angiographic results of RA grafts used for myocardial revascularization are excellent, superior to those achieved with the saphenous vein. A correct surgical indication (the use of this conduit to revascularize only vessels with severe stenoses) is essential. Continued therapy with calcium-channel antagonists after the first year and the performance of the proximal anastomosis to the ascending aorta do not influence the midterm angiographic status of RA grafts.
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References |
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TopAbstractIntroductionPatients and methodsResultsDiscussionReferences |
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